The present invention relates to a heating apparatus for heating an advancing yarn and which is particularly adapted for use in a yarn false twist crimping machine.
For crimping synthetic filament yarns in a false twist crimping machine, it is common to provide heaters, through which a yarn is guided. The yarn advances in a heatable axial channel, the target temperature of the yarn being in a range from 150.degree. C. to 230.degree. C. The heater is operated at a temperature, which is substantially higher than 300.degree. C. A heater may have several channels, each of which receives one yarn.
EP 0 412 429 B1 and corresponding U.S. Pat. No. 5,148,666 disclose a heater for a yarn false twist crimping machine, which has a heatable axial channel, through which the yarn advances along a zigzagged path. The zigzagged path is formed by several yarn guides, with one yarn guide being arranged at each reversal point of the line. The yarn guides are individual plates, which are inserted into the axial groove parallel to and equally spaced apart from one another.
In operation, the yarn guides of the above described heater will soil after a certain period of time, as a result of organic deposits and the like. To avoid an excessive deviation of the yarn guidance from a desired value, it is necessary to periodically remove and clean the yarn guides. In the known heater, each yarn guide must be removed individually, which is time consuming.
It is accordingly an object of the present invention to further develop the known heater such that the number of yarn guide elements is minimized, and the handling necessary for cleaning or changing of the yarn guides is simplified.